Interstitial pulmonary fibrosis is characterized in its early stages by an intense inflammatory cell infiltrate. To assess the relationship of the inflammatory process to the development of fibrosis the bronchoalveolar washings and lungs of hamsters and mice with experimental pulmonary fibrosis induced by intratracheal instillation of bleomycin will be evaluated for the presence of chemotactic factors for lymphocytes and neutrophilic polymorphonuclear leukocytes, employing a modified Boyden chamber assay. The secretions and extractions of bleomycin and saline challenged animals ' lungs will be studied at various time intervals after challenge to assess the longitudinal appearance of chemotactic factors while parallel histologic, physiologic and biochemical correlations are done at the same time. The sources of origin of neutrophil and lymphocyte chemotactic factors will be identified (i.e., complement, the alveolar macrophage, etc.) and the factors will be purified utilizing standard chromatographic techniques. Purified specific chemotactic factors will then be reinstilled intratracheally in normal animals to create inflammatory cell infiltrates of one unique cell type (either neutrophil or lymphocyte). The animals that have received specific intratracheal chemotactic factors will then be followed physiologically and histologically to evaluate the roles of the inflammatory cell types in the development of fibrosis. Lastly, pharmacologic manipulation directed at diminishing the inflammatory cell infiltrate by both inhibiting chemotactic factor generation and release, and target cell responsiveness will be assessed in vivo in the bleomycin induced animals and in vitro in Boyden chambers.